ALBANY - Long Island has rapidly emerged as key to control of the State Senate this fall, with Republicans and Democrats focusing on three races that have taken shape over the past month.

Republicans and Democrats will fight to fill the Suffolk County-based seat of Sen. Lee Zeldin (R-Shirley), who is running for Congress, and the primarily Nassau County-based seat of ex-Sen. Charles Fuschillo Jr., who took a job at a nonprofit. Further, Democrat Adam Haber's announcement on Thursday that he'll challenge Sen. Jack M. Martins (R-Mineola) makes another high-profile race in western Nassau.

"Long Island is going to be the main battleground for this year's elections," said Sen. Michael Gianaris (D-Queens), head of the Democratic Senate Campaign Committee. "There are certainly other races to watch. But to have so many vacant seats and other competitive seats makes it clear that Long Island will be the center of attention."

The Island races won't be the only ones to watch -- contests in the Hudson Valley, Capital Region and Western New York will be factors, too. But the Island races have come together more quickly. In the past month:

Republicans nominated Anthony Senft, a Conservative Party member and Islip town board member, to run in Zeldin's South Shore district. Adrienne Esposito, the executive director of Citizens Campaign for the Environment, filed to create a campaign committee and many expect her to emerge as the Democrat candidate. Democrat Joseph Fritz also has expressed interest.

Two Democrats said they want to run for the seat vacated by Fuschillo: Nassau County Legis. David Denenberg and Freeport Deputy Mayor Carmen Pineyro, setting up a possible primary. Republicans have nominated Nassau Legis. Michael Venditto, son of Oyster Bay Town Supervisor John Venditto.

advertisement | advertise on newsday

Haber, an East Hills businessman who self-financed his run for Nassau County executive last year, said he's jumping in the race against Martins.

Every seat counts in the politically split Senate. Currently, there are 32 Democrats and 29 Republicans, with two vacancies. But the Republicans and six breakaway Democrats control the chamber under an unusual power-sharing agreement. Though the coalition, led by Senate co-leaders Dean Skelos (R-Rockville Centre) and Jeff Klein (D-Bronx) expects to stick together, mainline Democrats are hoping they can pick up seats and change the dynamic.

Republicans counter that the coalition's ties are solid, nonpresidential years usually bode well for their legislative candidates, and Island residents historically have voted for GOP senators as a way to balance the State Legislature and keep New York City Democrats from dominating the agenda.

"Every Democrat who runs for the State Senate on Long Island is campaigning to join the same New York City-dominated conference that enacted the job-killing MTA payroll tax, eliminated the [property-tax] rebate check for seniors and homeowners, and shifted important school aid to New York City at Long Island's expense," said Scott Reif, a Skelos spokesman. "Senate Republicans have restored balance to state government, and remain Long Island's voice in Albany."

Democrats point out their party enrollment numbers have been growing steadily and they now have an enrollment advantage in the three districts. "The trend on Long Island has been Democrat for decades now," Gianaris said.

@Newsday

"Democrat advantages in a Republican year make for close races," said Hank Sheinkopf, a Democrat political consultant.

Republicans start with an advantage in each of the three races, said Lawrence Levy, executive dean of the National Center for Suburban Studies at Hofstra University.

Martins has the incumbency, name recognition and "an image of being very accessible to local officials, Democrats and Republicans alike," Levy said.

"The only thing that gives Adam Haber a chance is that, if he wants, he can match Martins dollar for dollar," Levy said.

Senft is in a district that traditionally favors Republicans -- Democrat Brian Foley won it in 2008 but lost to Zeldin in 2010. But Levy said Esposito has name recognition through her environmental work.

advertisement | advertise on newsday

Levy said the battle to replace Fuschillo could be the most intriguing. The Democrats have to settle on a candidate, but if it's Denenberg, he's "performed spectacularly well" in county elections. On the GOP side, "Venditto has a name that's very well known and respected in much of the district," Levy said.